<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="js/jquery.js"></script>
    <style>
        a:hover{
            background: #000;
            color: #ffffff;
        }

    </style>
</head>
<body>
<a id="ioi" class="iuy" href="#">123123123123</a>
<script>
//    document.getElementById("ioi").style="color:none;background:#ff0000;";
//
//    $("#div").addclass("aaa");
    $(".iuy").css("color","#f00")
</script>
</body>
</html>